Spread footer or pad under footer for wall point loads
Spread footer or pad under footer for wall point loads
(OP)
I am working with an architect here in central Florida who insists on using large reinforced concrete pads under standard 12"x20" monolithic footers for high point loads on exterior CMU walls. Vertical reinforcement is provided between the bond beam and footer - 3,000 PSI concrete filled cells with(1)#5 rebar for each 5,000 lbs of reaction load. The vertical reinforcement is extended down into the pad.
I am accustomed to using spread/bell footers under the point loads with the width determined by the magnitude of the point load and the depth at the standard 20". The load bearing capacity of our sandy soils is typically 1,500 to 2,000 PSF, but tests are seldom done to verify the capacity for residential construction.
Any thoughts that you have regarding the need for a pad under the standard footer vs just spreading the width of the footer would be appreciated.
I am accustomed to using spread/bell footers under the point loads with the width determined by the magnitude of the point load and the depth at the standard 20". The load bearing capacity of our sandy soils is typically 1,500 to 2,000 PSF, but tests are seldom done to verify the capacity for residential construction.
Any thoughts that you have regarding the need for a pad under the standard footer vs just spreading the width of the footer would be appreciated.






RE: Spread footer or pad under footer for wall point loads
What he wants to do is also requiring two separate pours - more expensive and time consuming for the contractor and owner.
I would politely tell the Architect to do the architecture and let you do the structural engineering. That's the expertise he is paying you for. He should listen to the advice if he is smart. I know. I'm asking for the moon.
Mike McCann
McCann Engineering
RE: Spread footer or pad under footer for wall point loads
RE: Spread footer or pad under footer for wall point loads
You have not mentioned, why the architect is asking you to provide this enlarged pad?
RE: Spread footer or pad under footer for wall point loads
csd
RE: Spread footer or pad under footer for wall point loads
RE: Spread footer or pad under footer for wall point loads
Regarding filled cells: In the 110 MPH wind load areas (most of central Florida), we call for: Vertical reinforcement 6’ o.c. max, 3000 psi conc, (1) #5 w/10” std hook, 25” min overlap from footer to bond beam and located at all corners, openings, beams, and girders.
RE: Spread footer or pad under footer for wall point loads
RE: Spread footer or pad under footer for wall point loads
h
My concern is that a lot of the point load is distributed to the regular 12"x20" footer rather than the pad beneath. I like the pad design when it is used as a stiffner under a floor slab to aupport a column because there is no footer that absorbs the load.